We propose to develop and effective mode of chemotherapy for hepatocellular carcinoma based on the use of hepatotoxins in combination with specific targeted-antagonists to achieve exclusive rescue of normal hepatocytes. This targeting will be dependent on the known ability of normal hepatocytes, and the inability of the majority of hepatocellular carcinomas to take up and degrade, intracellularly, galactose-terminal glycoproteins by a specific receptor-mediated endocytosis. Linkage of antagonist to appropriate glycoproteins could result in specific binding and release of antagonist with subsequent rescue of only receptor (+), differentiated cells. We will first test our hypothesis usin a cell-culture system of Hep G2, receptor (+) and PLC/PRF/5, receptor (-) cells as a model of hepatocellular carcinoma. Three different toxin-antagonist pairs will be examined. Various chemical coupling methods will be studied in the preparation of antagonist-glycoprotein conjugates. Using established methods, these conjugates will be tested for cellular uptake and internalization. Cell cultures will also be used to determine efficacy of asialoglycoprotein-antagonist conjugates in achieving exclusive rescue of receptor (+) cells by administration of conjugates to toxin-treated cells. The mechanism of rescue will be established biochemically. Asialoglycoprotein-antagonist conjugates found to achieve specific rescue in vitro will be tested in vivo, using normal rats to determine if they can prevent or decrease hepatic damage caused by a defined hepatotoxic dose of the corresponding toxin. Destruction of recepto (-) and specific rescue of receptor (+) cells by combined use of toxins and asialoglycoprotein-antagonist conjugates will be tested in two in vivo models: (1) Hep G2 and PLC/PRF/5 implants in rnu/rnu nude rats and (2) carcinogen-induced hepatocellular carcinoma in rats.